Neuronal characterization, compartmental distribution, and activity- dependent regulation of glutamate immunoreactivity in adult monkey striate cortex

Abstract

Monospecific antibodies to glutamate were used to characterize the organization of excitatory neurons and the plasticity of glutamate expression in the macaque striate cortex. Somata and processes immunoreactive for glutamate were densely and unevenly distributed in layers II-III, IVA, IVC. In tangential sections through layers II and III, patches of intense glutamate immunostaining were observed and were found to coincide with regions of the cytochrome oxidase (CO)-rich puffs. By contrast, clusters of intense immunostaining were surrounded by the lightly immunostained but intensely CO-stained lattice in layer IVA. Similarly, in layer IVC, focal aggregates of intense glutamate immunoreactivity were interspersed among regions of light immunostaining but intense CO staining. Glutamate immunoreactivity was also intense in layer VI but was much lighter in layers I, IVB, and V. Throughout the striate cortex, neurons resembling pyramidal cells and spiny stellate cells and processes that included dendrites and axons were immunostained. None of the glutamate-positive neurons was GABA immunoreactive. Following monocular deprivation of adult monkeys by intravitreal injections of TTX into one eye, glutamate immunoreactivity in layers IVC was distributed in alternating intensely and lightly stained stripes. The stripes of reduced immunostaining, which contained an abnormally low concentration of glutamate neurons and pale neuropil, corresponded to columns dominated by the TTX-injected eye. Similar stripes of alternating intense and light immunoreactivity were seen in layers II-III, where they corresponded to rows of puffs at the centers of intact-eye and deprived-eye columns, respectively. These findings demonstrate that glutamate-immunoreactive neurons and terminals in monkey striate cortex are densely concentrated in layers receiving direct geniculocortical innervation. In addition, the glutamate neurons and terminals form discrete units, which in layers II and III coincide precisely with regions receiving geniculocortical terminations but in layers IVA are segregated from these terminations. The findings also indicate that glutamate immunoreactivity is regulated by visually driven activity, and suggest that monocular deprivation in adulthood leads to a reduction in the major excitatory neurotransmitter in visual cortex as well as previously indicated reductions in GABA, the major inhibitory neurotransmitter.

Polarity-Sensitive Modulation of Cortical Neurotransmitters by Transcranial Stimulation

“…We therefore interpret the reduction in glutamate following cathodal stimulation as a consequence of a decreased rate of glutamate synthesis from glutamine with reduced excitatory neuronal transmission. This relationship has been observed in animal models, where experimentally altering the rate of neuronal activity leads to changes in neuronal-glial glutamate/glutamine cycling (Carder and Hendry, 1994).…”

Thoughts on the development, structure and evolution of the mammalian and avian telencephalic pallium

“…Recently, we learned that the striatal primordium participates with the medial ganglionic eminence (pallidal primordium) in generating massive streams of inhibitory interneurons that migrate both subventricularly and subpially into the cortex (De Carlos et al 1996;Anderson et al 1997;Lavdas et al 1999;. Note that thalamorecipient layer IV interneurons are thought to be mainly excitatory (Valverde 1985;Freund et al 1985;Carder & Hendry 1994;Lund et al 1994). These migratory streams are not known to have any directional or target-layer speci¢city.…”

Synapses, spines, zinc and pathology of Alzheimer's disease.

“…These pyramidal cells are found to be gutamatergic (Carder and Hendry, 1994) and zincergic as well (Brown and Dyck 2005;Miyashita et al, 2007). Pyramidal cells are found in all cortical areas.…”

“…These pathways are thought to be responsible for the responses to visual stimuli complete that can exist in (Lund et al, 1975;Katz 1987;Buhl and Singer, 1989;Hubener et al, 1990;Einstein and Fitzpatrick, 1991). Their interlaminar and collateral horizontal connections provide synaptic contact with other cortical neurons (Gilbert andWiesel, 1979, 1983;Martin and Whitteridge, 1984;Carder and Hendry, 1994) in layers II, III, V and IV, creating the basic circuit across different areas of cortex (Feldman, 1984;Martin and Whitteridge, 1984;Carder and Hendry, 1994).…”

“…Within these cortical areas, which includes V1, the spiny stellate cells are restricted to layer IV where they receive thalamocortical innervation. From there, spiny stellate cells can send some axons into other areas of the cortex, but the majority form exclusively intracortical connections with neurons in the superficial layers (Lund, 1973;Carder and Hendry, 1994). Interneurons can be differentiated by anatomical, physiological and molecular criteria (for review, Petilla Interneuron Nomenclature Group, 2008).…”